[F8] please help with action script( slideshow)

well ppl from flashkit i have a big problem that is givin me a headhache
i created a slideshow from a tutorial and it worked realy good but at the part with the action script i have problem with the numbers (-98 / -33) how do they work?!?

onClipEvent (mouseMove) {
xmousepos1 = _xmouse;
ymousepos1 = _ymouse;
if (xmousepos1>xmousepos2 && ymousepos1>-98 && ymousepos1<-33) {
_root.scrollclip.nextFrame();
}
if (xmousepos1-98 && ymousepos1<-33) {
_root.scrollclip.prevFrame();
}
if (ymousepos1<-98 || ymousepos1>-33) {
play ();
}
xmousepos2 = _xmouse;
ymousepos2 = _ymouse;
}



i put that code but those numbers -98 and -33... how can i know what are the right numbers for my movieclip?( the tutorial said i have to change them depending on my movieclip please help me)